At a private school in Newark, N.J., students dine daily on ingredients grown on the building’s roof. In Baltimore, city schools have their own 33-acre organic farm, while in Riverside, Calif., elementary school students trundle wheelbarrows of lettuce and buckets of strawberries from a community garden behind the playground directly to their own salad bar.

Across the United States, efforts to make school lunches more environmentally friendly have paired with the local food movement, as educators try to reconnect children with the growing season. School lunchrooms are also getting revamped to cut water and energy use and lessen food waste.

Although not every college can get all its milk, yogurt, and sour cream from its own herd of cows (as does the University of Illinois at Urbana-Champaign), or cage-free eggs from its own hens (as does Vermont’s Green Mountain College), dozens of universities are doing away with that rectangular symbol of the cafeteria: the tray. It’s a simple change, but one that school administrators say can dramatically reduce waste.

For example, the University of Illinois studied the environmental impact of eliminating trays in a dining hall that served an average of 1,300 students per day. “Not having trays saves 516 gallons of water a day – that’s 110,940 gallons in an academic year,” says Kristen Kirsten Ruby, assistant director of housing for marketing.

In addition to the water saved, the dining hall also used 473 pounds less dishwashing detergent that year. Even more interesting, Ms. Ruby adds: “We also noticed a 40 percent reduction in the amount of food waste.” Because students couldn’t carry as much, she explains, they didn’t take more than they could eat.

ARAMARK, a food-service provider for some 600 institutions of higher education, conducted a survey of 25 schools that found that trayless dining reduced waste by an average of 25 to 30 percent. When it asked 92,000 students at 300 colleges about getting rid of trays in cafeterias and dining halls, 75 percent said they were in favor of the change.

But the range of initiatives is as varied as the institutions. “We’re at the pioneering stage,” says David Krueger, codirector of the sustainability program at Baldwin-Wallace College in Berea, Ohio. “All of these bottom-up local initiatives [on college campuses] mimic the larger sustainability movement. It’s a carbon copy of trends across the spectrum.”

The University of Illinois, which already has its own apple orchard, is breaking ground on a 10-acre farm this summer – complete with frost protection to extend the growing season – that it hopes will be able to supply up to 50 percent of its vegetable needs.

The school is also moving forward with other ecofriendly efforts: A composting program will be started at the same time as the vegetable garden. And for the past three years, facilities management vehicles have run on cooking oil collected from dining halls.

“I don’t think we’re done,” says Ruby, noting that the university plans to roll out trayless dining in more of its halls. “Sustainability is definitely a continuing work in progress.”

At the University of California, San Diego, each student is given a reusable water bottle at the beginning of the school year. Also this year, dining services eliminated styrofoam and plastic utensils. If students want takeout, it comes with real plates and silverware.

“This system has been successful because Housing and Dining Services teamed up and created drop-spots at each dorm and apartment complex where students can leave their dirty dishes and utensils,” explains Christine Clark, a communications specialist for the university, in an e-mail. “Dining Services picks up the used dish ware daily.” Also, the dining halls all serve Fair Trade sugar, coffee, tea, and chocolate.

While no one is saying that fast food has lost its place as a staple of college all-nighters, the impact from green initiatives have the potential to continue years after graduation day, says Dr. Krueger. “In the sense that colleges and universities are incubators for ideas and forming the next generation of minds and lives, modeling practices that they can take with them is the most important thing we can do.”

Some students may already have been introduced to more sustainable lunchrooms long before they arrive at college. “There is huge variety in how schools are approaching this,” says Michal Ann Strahilevitz, an associate professor of marketing at San Francisco’s Golden Gate University, who studies “green” behavior, in an e-mail.“The key is not just giving [students] greener choices, but teaching them as well,” she explains.

At St. Philip’s Academy in Newark, students used to bring fast food and Lunchables for their midday meal. “Before, what came out of here as a result of three lunch periods to the dumpster was just incredible,” says Miguel Brito, the head of the Episcopal academy, which prepares low-income children for college prep schools.

To improve its students’ eating habits and teach the 350 K-8 children about growing seasons and farms, St. Philip’s radically redesigned its cafeteria program two years ago, when it moved into its new LEED-certified building, a converted chocolate factory. It arranged to buy local produce from two nearby farms and created a mandatory lunch program that would take advantage of the fresh fruits and vegetables.

One of the building’s most eye-catching environmental features is the gym’s green roof – 4,500 square feet of teaching gardens, complete with rain barrels to recycle water.

The program costs $750 a school year, which administrators says works out to less than $4 per meal, or roughly the cost of a Happy Meal.

“We thought we would hear that ‘We hate this food, we want to go back to McDonald’s,’ ” says Jennifer Kotkin, ecospaces coordinator and seventh-grade science teacher.

Instead, administrators say, the kids really enjoy eating what they have grown and are piling hummus and tzatziki on their plates along with PB&J.

The cafeteria also switched from speed lines with trays to family-style dining. “If you compare a normal school cafeteria to a family-style system, the percentage of waste significantly drops,” says Ralph Walker, the architect who designed the school’s new building. “Every individual student can control [his or her] own portions. You can make closer to the exact amount of food [needed], wash less, and do less.”

The students now eat off real china, and each one is assigned a task to help set or clear the table. Food waste goes either to a composter in the kitchen, which turns it into fertilizer for the garden, or to bins in the classrooms, where worms happily munch on leavings.

These days, “we use paper napkins that are [made from] recycled material. Other than that, we have no waste,” says Frank Mentesana, ecospaces facilitator.

Mr. Brito estimates that trash has been reduced by up to 90 percent.

“We even recycle the food that’s left over,” adds Ms. Kotkin. “We have a charity across the street ... and we bring them our leftover food to feed the homeless.”

For public schools, practical considerations weigh equally with idealistic ones. It costs about $1,500 a year for Emerson Elementary in Riverside, Calif., to run the school’s portion of a two-acre community garden. Principal John McCombs pays for the costs out of the lettuce he sells the district for 50 cents a head.

He has a little tougher time maximizing profits from the school’s 1,000 strawberry plants, because his pint-sized pickers enjoy sampling the wares. “It’s a fun problem to have,” he says. “One good thing, [the farming program] helps the students reduce waste and not pile their plate full of food. They know how much work it took to grow the food, know how much water it takes.”

Pioneers of the farm-to-school movement, such as Rodney Taylor, say that such programs have proven economical as well as environmentally viable. In Santa Monica, Calif., where he instituted school composting and recycling programs along with salad bars heaped with locally grown produce, the cost of the meals went from 70 cents to 58 cents after three years, thanks to, among other things, a big reduction in garbage costs.

It’s all a matter of introducing this way of eating while kids are young, says Mr. Taylor, now the director of nutrition services for the Riverside Unified School District, about 60 miles east of Los Angeles. “If we get them early and teach them, we’ve got a chance.”